Semiconductor component

ABSTRACT

A semiconductor component is disclosed. One embodiment provides a semiconductor body having a cell region with at least one zone of a first conduction type and at least one zone of a second conduction type in a rear side. A drift zone of the first conduction type in the cell region is provided. The drift zone contains at least one region through which charge carriers flow in an operating mode of the semiconductor component in one polarity and charge carriers do not flow in an operating mode of the semiconductor component in an opposite polarity.

CROSS-REFERENCE TO RELATED APPLICATIONS

This Utility patent application claims priority to German PatentApplication No. DE 10 2006 050 338.4 filed on Oct. 25, 2007, which isincorporated herein by reference.

BACKGROUND

The present invention relates to a semiconductor component. In oneembodiment, a semiconductor component is provided, having a soft diodebehavior.

For a fast and low-loss switching behavior, the behavior ofsemiconductor structures is intended to proceed such that it is as“soft” as possible. The semiconductor component can be an IGBT withbackward diode.

The description is given on the basis of an IGBT, but this does notsignify any restriction. Rather, a “semiconductor component” can also beunderstood to mean for example a combination of an IGBT with a MOSFET ora Schottky diode.

For an IGBT which can be operated in a diode operating mode and in anIGBT operating mode, a diode operating mode can usually take place inopposite polarity with respect to the actual IGBT operating mode.

IGBTs configured in this way with RC-IGBT structures (reverse conductingIGBT structures) upon turn-on initially operate in a MOSFET operatingmode, that is to say in a unipolar operating mode, in which no holeinjection takes place from the rear side of the semiconductor body. Itis only at higher currents that the rear-side p-conducting emitter zoneturns on, such that holes are injected into the drift path and thesemiconductor component then operates in the IGBT operating mode, thatis to say a bipolar operating mode.

The changeover from the unipolar operating mode to the bipolar operatingmode takes place when the electrons, which are the sole charge carriersof the current in the unipolar operating mode in the drift path andwhich flow away upstream of the p-conducting emitter zones transverselyto the nearest n-conducting zone, produce an ohmic voltage drop upstreamof the p-conducting emitter zones, which voltage drop excites thep-conducting emitter zones to effect a hole injection. The voltage dropmust be approximately 0.7 V at room temperature.

This can mean that the current at which the changeover from the unipolaroperating mode to the bipolar operating mode takes place can depend onthe doping of the rear-side n-conducting emitter zones within the p-typeemitter zones and can moreover likewise depend appreciably on thegeometrical arrangement of the p-conducting and/or the n-conductingemitter zones: the greater the distance from one n-conducting zone tothe next n-conducting zone on the rear side of the semiconductor body,the smaller the current possibly becomes which is required to producethe voltage drop of approximately 0.7 V.

It can follow from this that p-conducting emitter zones that are as wideas possible can be expedient for good on-state properties of thesemiconductor component.

Simply enlarging the p-type zones can lead to widely distributed n-typezones, however. It may be desirable for the latter to be as close to oneanother as possible in order to be able to utilize the correspondingvolume of the cell region of the semiconductor body or the correspondingcross-sectional region thereof for the diode operating mode.

The requirement of good on-state properties of the semiconductorcomponent on account of wide p-conducting zones and n-conducting zonesthat are close together for a high current flow in the diode operatingmode apparently cannot readily be fulfilled simultaneously with therequirements made with regard to a high diode softness or a lowswitching power loss.

One possibility for obtaining a soft diode behavior may be to reduce thelocal charge carrier lifetime near the front-side anode of theintegrated diode. The anodal carrier flooding can thereby be reduced,which results in an increased diode softness. What is more, the reversecurrent peak and the total storage charge are reduced. However, thismethod has the effect that the collector-emitter saturation voltageVCESat increases as the reduction of the charge carrier lifetimeincreases. As a result, the degree of charge carrier lifetime reductionis limited since the on-state losses also increase with the increase ofVCESat, which can lead to an excessively great heating of thesemiconductor component.

A further approach for improving the diode softness may be to increasethe doping concentration of the rear-side n-type emitter zone. Therear-side carrier flooding thereby increases, which increases thesoftness. However, this can in turn result in an increase in the storagecharge and, consequently, in increasing switching losses of the diodeand in increasing turn-on losses of the IGBT.

For these and other reasons, there is a need for the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of embodiments and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments andtogether with the description serve to explain principles ofembodiments. Other embodiments and many of the intended advantages ofembodiments will be readily appreciated as they become better understoodby reference to the following detailed description. The elements of thedrawings are not necessarily to scale relative to each other. Likereference numerals designate corresponding similar parts.

FIG. 1 illustrates a sectional illustration through an IGBT of planarembodiment.

FIG. 2A illustrates a sectional illustration through an IGBT of trenchembodiment according to one embodiment.

FIG. 2B illustrates a sectional illustration through the IGBT from FIG.2A in the diode operating mode.

FIG. 3 illustrates characteristic curves of charge carrierconcentrations in the course between front side and rear side of an IGBTaccording to the embodiment of FIGS. 2A and 2B.

FIG. 4A illustrates a sectional illustration through an IGBT of trenchembodiment according to a further embodiment.

FIG. 4B illustrates a sectional illustration through the IGBT from FIG.4A in the diode operating mode.

FIG. 5 illustrates a sectional illustration through an IGBT according toa further exemplary embodiment in the diode operating mode.

FIG. 6A illustrates a sectional illustration through an IGBT accordingto a further exemplary embodiment.

FIG. 6B illustrates the characteristic curve of the electric fielddistribution between front side and rear side of an IGBT according to anembodiment according to FIG. 6A.

FIG. 7A illustrates a sectional illustration through an IGBT accordingto a further exemplary embodiment in the diode operating mode.

FIG. 7B illustrates a sectional illustration through an IGBT accordingto a sixth exemplary embodiment in the diode operating mode.

FIG. 8A illustrates a plan view of structures of n-conducting zones inthe cell region of a semiconductor arrangement.

FIG. 8B illustrates a plan view of structures of n-conducting zones inthe cell region of the semiconductor arrangement.

FIG. 8C illustrates a plan view of structures of n-conducting zones inthe cell region of the semiconductor arrangement.

FIG. 8D illustrates a plan view of structures of n-conducting zones inthe cell region of the semiconductor arrangement.

FIG. 9A illustrates a plan view of structures of n-conducting zones inthe cell region of the semiconductor arrangement.

FIG. 9B illustrates a plan view of structures of n-conducting zones inthe cell region of the semiconductor arrangement.

FIG. 9C illustrates a plan view of structures of n-conducting zones inthe cell region of the semiconductor arrangement.

FIG. 9D illustrates a plan view of structures of n-conducting zones inthe cell region of the semiconductor arrangement.

FIG. 9E illustrates a plan view of structures of n-conducting zones inthe cell region of the semiconductor arrangement.

FIG. 9F illustrates a plan view of structures of n-conducting zones inthe cell region of the semiconductor arrangement.

FIG. 9G illustrates a plan view of structures of n-conducting zones inthe cell region of the semiconductor arrangement.

FIG. 9H illustrates a plan view of structures of n-conducting zones inthe cell region of the semiconductor arrangement.

FIG. 9I illustrates a plan view of structures of n-conducting zones inthe cell region of the semiconductor arrangement.

FIG. 9J illustrates a plan view of structures of n-conducting zones inthe cell region of the semiconductor arrangement.

DETAILED DESCRIPTION

In the following Detailed Description, reference is made to theaccompanying drawings, which form a part hereof, and in which is shownby way of illustration specific embodiments in which the invention maybe practiced. In this regard, directional terminology, such as “top,”“bottom,” “front,” “back,” “leading,” “trailing,” etc., is used withreference to the orientation of the Figure(s) being described. Becausecomponents of embodiments can be positioned in a number of differentorientations, the directional terminology is used for purposes ofillustration and is in no way limiting. It is to be understood thatother embodiments may be utilized and structural or logical changes maybe made without departing from the scope of the present invention. Thefollowing detailed description, therefore, is not to be taken in alimiting sense, and the scope of the present invention is defined by theappended claims.

It is to be understood that the features of the various exemplaryembodiments described herein may be combined with each other, unlessspecifically noted otherwise.

The “first conduction type” is to be understood hereinafter to mean then conduction type, in which n-type charge carriers are majority chargecarriers. However, it is expressly emphasized that the first conductiontype can, if appropriate, also be the p conduction type, in which p-typecharge carriers are majority charge carriers.

In one exemplary embodiment of a semiconductor component, the rear sideis structured in such a way that the drift zone contains in the cellregion at least one region through which charge carriers do not flow inthe diode operating mode of the semiconductor component, but throughwhich charge carriers can flow in the IGBT operating mode. Chargecarriers can flow through at least one further region within the driftzone both in the diode operating mode and in the IGBT operating mode.

Such a structuring of the rear side of the semiconductor component leadsto an effective diode area which is smaller than the area of the cellregion or smaller than the IGBT area. Diode softness can thereby beachieved by using an increased doping of the n-type diode emitter zoneswithout the storage charge increasing.

It is thus possible for the p- and n-type zones to be structured withinthe effective diode zones in such a way that a changeover from aunipolar to a bipolar operating mode already takes place at lowcurrents.

A suitable structuring can be achieved by virtue of the fact that atleast one of the zones of the second conduction type contains a regionconfigured in such a way that the minimum distance from the center ofthe region as far as that zone of the first conduction type which isclosest to it is substantially greater than the corresponding minimumdistance in the remaining zones or regions of the second conductiontype.

In order to realize this minimum distance set as “substantiallygreater”, it is possible for the zones of the first conduction type tobe distributed virtually over the entire rear side of the semiconductorcomponent and in one embodiment also in the cell region. Triggeringregions which can bring about the changeover from the unipolar to thebipolar operating mode are simultaneously created here by thep-conducting emitter zones which are widened on account of the greaterminimum distance.

The rear side of the semiconductor component can be subdivided intodifferent regions. One region includes rear-side zones both of the firstand of the second conduction type, while a second region includesexclusively rear-side zones of the second conduction type. It is alsopossible for a plurality of first and/or a plurality of second regionsto be present.

The rear side of the semiconductor component can be configured in such away that the minimum distance from the center of the at least onepreferably p-conducting zone as far as the n-conducting zone which isclosest to it or as far as the edge termination of the component issubstantially greater than the corresponding minimum distance in theremaining p-conducting zones. “Substantially greater” can mean that thedistance is at least a factor of 1.5 to 5 or more greater than the restof the distances. Therefore, a uniform distribution of the respectivezones is not present, under certain circumstances.

By using different dimensions (widths) for the p-conducting zones on therear side of the semiconductor body, it is possible to achieve arestricted flowing of charge carriers through the drift zone in thediode operating mode, good IGBT properties, namely a triggering of thep-conducting zones at sufficiently low currents, and at the same timealso particularly good diode properties, namely a high current flowthrough n-conducting emitter areas.

Continuous zones having identical distances between the n-type emitterzones with adjoining or intervening zones without n-type emitter zonescan bring about the desired ensuring or restriction of the chargecarrier flooding in different operating modes of the semiconductorcomponent.

At least one region of the drift zone through which charge carriers donot flow in the diode operating mode can be achieved by virtue of theeffective diode area being smaller than the area of the cell region orthe IGBT area.

The actual diode area and the effective diode area emerge as followsfrom the above-described manner of arranging the p- and n-type zones.The actual area of the diode can correspond to the area of the rear-siden-type emitter zones. The effective diode area is for example the actualdiode area together with that area of the drift zone outside the actualdiode area which is flooded by charge carriers in the diode operatingmode. This corresponds, therefore, to the maximum cross-sectional areain the plane of the semiconductor body of that volume in the drift zonethrough which charge carriers flow in the diode operating mode. Theeffective diode area, on account of the described arrangement of therear-side emitter zones, can be smaller than the cell region, that is tosay smaller than the area which is active in the bipolar operating modeof the IGBT—also referred to as IGBT area above—which corresponds to thetop area of the drift zone.

To put it clearly, the rear side of the semiconductor body can containat least one first region having zones both of the first and of thesecond conduction type and also at least one second region having zonesof the second conduction type. In this case, the at least one secondregion can have a partial area which includes at least one circular areawhich is so large that there lie within the at least one second regionsubregions which are so far away from adjacent emitter zones of thefirst conduction type or from an edge zone of the semiconductor bodythat no charge carrier throughflow takes place within the subregions inthe at least one second region in the diode operating mode. Thesearrangements can ensure, under certain circumstances, that thesemiconductor body has within the drift zone regions through whichcharge carriers flow in a forward operating mode and in a reverseoperating mode of the semiconductor component, and that it has otherregions through which charge carriers flow only in one operatingdirection. The latter region occurs for example when only one regionthrough which charge carriers flow in both operating modes is presentwithin the drift zone. This corresponds, therefore, to the presence ofonly one region having zones both of the first and of the secondconduction type.

In one embodiment of the semiconductor component, the size of theeffective diode area is between 25 and 75 percent of the area of thecell region.

In another embodiment of the semiconductor component, it is possible forthere to be no region in which the effective diode area overlaps an edgetermination structure of the cell region, thereby preventing formationof an electron-hole plasma below the edge in the diode operating mode.This can have the consequence of preventing an accumulation of p-typecharge carriers (holes) below the edge structure. Consequently, norestriction of the reliable operating region of the diode occurspossibly at high switching speeds.

In a further embodiment, the softness of the diode can be set by usingthe doping concentration of the first conduction type in the associatedrear-side emitter zone. The diode softness can be improved by increasingdoping magnitude of the rear-side n-type emitter zones.

Switching losses attributed to an increased doping of the n-type emitterzone can be minimized, under certain circumstances, by theabove-described reduced effective diode area in comparison with the areaof the cell region or the upper area of the drift zone, since one or aplurality of regions through which charge carriers do not flow in thediode operating mode exist within the drift zone in the diode operatingmode. In this case, under certain circumstances, the diode softness canbe improved by the increased doping concentration in the n-type emitterzone, however, such that the apparent contradiction between minimumswitching power loss and maximum diode softness can now be resolved.

In a further embodiment, the diode softness is increased by an increaseddoping of the n-type emitter zones by doses of between 10¹⁵1/cm² and10¹⁶1/cm².

In a further embodiment, a more extensive reconciliation of the criteriaor the target conflicts is achieved by virtue of the fact that furtherp-type zones, which are laterally delimited, are disposed upstreamdirectly in front of the n-type emitter zones. In this case, the p-typezones can have the same width as the adjoining n-type zones, but canalso be substantially smaller or larger than them. In this case, thevertical extent of the p-type zones can be chosen with a magnitude suchthat they reach precisely as far as the junction between a field stopzone and the drift zone, project beyond it, or do not project beyond it.The diode softness can only be improved to a certain extent by using thedoping magnitude of the n-type emitter zones. By using the p-type zonesdisposed upstream, it is possible to form further diodes with highlydoped p- and n-type zones whose field punch-through in the case of achopping of the current as a result of too little residual plasma in thesemiconductor structure increases or re-establishes the diode softness.

In the event of a great increase in the electric field at the pnjunction between n-type emitter zones and the p-type zones disposedupstream, an avalanche-multiplicative generation of electron-hole pairscan take place, whereby a continuous current flow or a soft commutationbehavior can be ensured, whereas current chopping could otherwise occurin this case as a result of the depletion of the storage charge.

This can give rise to an additional degree of freedom for the increasein the diode softness independently of the doping concentration.

In a further embodiment, a reconciliation of the above-mentionedcriteria can also be achieved by virtue of the fact that the drift zonehas a local charge carrier lifetime zone having a greatly reduced chargecarrier lifetime in comparison with the charge carrier lifetime in therest of the drift zone. This zone does not have to extend over theentire thickness of the drift zone, but rather can be thinner. This canlead to a reduction of the storage charge in the diode. As a result,under certain circumstances, as described above, the switching powerloss can be reduced without an excessively great undesired alteration ofthe saturation voltage of the IGBT.

A further charge carrier lifetime zone having a third charge carrierlifetime can also be arranged directly below the thin charge carrierlifetime zone having a greatly reduced charge carrier lifetime, whichzone has a weakly reduced charge carrier lifetime, in the drift zone.

The charge carrier lifetime zone having a greatly reduced charge carrierlifetime and the further charge carrier zone having a weakly reducedcharge carrier lifetime can extend over the entire area of the driftzone, or else only over the corresponding effective diode area.

This local charge carrier lifetime zone can be delimited to the regionof the effective diode area.

FIG. 1 illustrates a sectional illustration of an IGBT including asemiconductor body 1, composed of silicon. Other materials, such as, forexample, silicon carbide, AIII-BV semiconductors, etc. can also bechosen instead of silicon. The semiconductor body 1 has on its frontside Vo—incorporated into an n-conducting drift zone 2—in a cell region3 p-conducting body regions 4, in each of which n-conducting sourcezones 5 are provided. There are provided on the surface of the frontside of the semiconductor body 1 an insulating layer 6 composed ofsilicon dioxide, for example, and a metallization 7 composed ofaluminum, for example, which makes contact with the body region 4 andthe source zones 5. There are also incorporated into the insulatinglayer 6 gate electrodes 8 composed of polycrystalline silicon, forexample, which produce a channel 9 when a voltage is applied between thesource zone 5 and the drift zone 2. The metallization 7 extends as faras an edge region 10 containing one or a plurality of p-conducting rings11, for example. In the edge region 10, a thick oxide, which is notdesignated in any further detail, is also situated on the insulatinglayer 6.

There are provided in the rear side Rü of this IGBT p-conducting zones12 and n-conducting zones 13, which can have substantially identicaldimensions and which are provided with a rear side metallization 14.

FIG. 2A illustrates one embodiment of the semiconductor component in itscell region with a semiconductor body 1 composed of silicon, forexample, a drift zone 2, body regions 4, source zones 5, insulatinglayers 6 composed of silicon dioxide, for example, metallizations 7composed of aluminum, for example, gate electrodes 8, p-conducting zones12, 15 and n-conducting zones 13. In the case of this trench IGBT, thezones 13 are provided with an n-type doping. A field stop zone 17 isadditionally situated in front of the p- and n-type zones 10 and 11,respectively, but it can also be omitted. The p-conducting zones andn-conducting zones have different dimensions. A first rear-side zone 18is illustrated here, having p-conducting zones 12, 15 and n-conductingzones 13. A second rear-side region 19 only has p-conducting zoneswithout n-conducting zones.

The trench embodiment is not mandatory, however, that is to say that allthe embodiments and principles described below can also be applied tothe planar embodiment of FIG. 1, where a field stop zone can likewise beprovided.

The n-conducting zones 13 are configured for example in punctiform orcircular fashion and form structures, such that the individual points ofthe structures represent rectangles or polygons, for example.

For the sake of better understanding of the figures, it is pointed outthat the size relationships do not necessarily accord with reality. Thespacings of the zones 12, 13 and of the gate electrodes 8 are not trueto scale, under certain circumstances.

The semiconductor component from FIG. 2A in the diode operating mode isillustrated in FIG. 2B. Two regions 2 a, 2 b arise, wherein no chargecarrier flooding takes place within the drift zone in the region 2 a inthe diode operating mode, while charge carriers flow through the region2 b. Charge carriers can flow completely through at least the region 2 bin an IGBT operating mode of the semiconductor component as well. Afirst region 18 having p-type zones 12, 15 and n-type zones 13, and alsoa second region 19 having p-type zones 15 and without n-type zones 13are illustrated. The second region 19 is so large that it contains asubregion 33 that is so far away from adjacent emitter zones 13 of thefirst conduction type that no charge carrier throughflow takes placewithin the subregion 33 in the diode operating mode.

FIG. 3 illustrates a plurality of charge carrier profiles for diodeoperating modes of possible semiconductor components in order toillustrate the relationship of different measures and their effects. Thecharge carrier concentration LK is plotted against the zone betweenfront side Vo (“anode”) and rear side Rü (“cathode”) of thesemiconductor component. A curve 20 illustrates the behavior of a diodethat is to be designated as soft, in the case of which behavior thecarrier concentration increases toward the rear side Rü without abruptchanges. A curve 21 illustrates the profile of a customary RC diode incomparison therewith. A curve 22 illustrates the effect of a localcarrier lifetime reduction. A—considered locally—rapid decrease in thecarrier concentration (arrow P) near the front side Vo and a uniformincrease again toward the rear side Rü occur here. A curve 23furthermore illustrates the effect of an increase in the dopingconcentration of the rear side n-type emitters. The charge carrierconcentration at the rear side Rü is thereby increased (arrow P′).

The semiconductor component in accordance with FIG. 4A has essentiallythe same zones and regions as in the exemplary embodiments of FIGS. 2Aand 2B. It differs from the exemplary embodiments, however, in that therear-side n-conducting zones 13 spread over the whole area but at thesame time are not distributed uniformly: n-conducting zones 13 areincorporated into a p-conducting environment (12, 15) in such a way thatp-conducting zones (12, 15) arise, wherein the zones 15 are embodied insuch a way that the minimum distance 25 from their center to the closestn-conducting zone 13 is substantially greater than the correspondingsecond minimum distance 25 a in the remaining zones of the p-conductiontype 12. Therefore, at least two first regions 18 having grouped oruniformly distributed p-conducting zones 12 and n-conducting zones 13,the first regions being distributed over the rear side Rü of the cellregion of the semiconductor component, and also at least one secondregion 19 having one or more continuous p-conducting zones 15 withoutn-conducting zones 13 arise.

FIG. 4B illustrates how the drift zone is divided into at least oneregion 2 a and at least one further region 2 b in the diode operatingmode of a semiconductor component from FIG. 4A. In the diode operatingmode, majority charge carriers flow through the at least one region 2 b,whereas no charge carrier throughflow takes place in the further region2 a. Charge carriers flow completely through the regions 2 b in the IGBToperating mode of the semiconductor component, however. Charge carriersflow almost completely or completely through the regions 2 a in the IGBToperating mode.

FIG. 5 illustrates a semiconductor component according to FIGS. 2A and2B in the diode operating mode. The edge region 10 is also representedhere in order to illustrate that the region 2 b with a charge carrierthroughflow in the diode operating mode does not have to extend to belowthe edge region 10 or to beyond the cell region 3. It likewise becomesclear here that charge carriers do not have to flow completely throughat least one region 2 a which extends to below the edge region 10 in adiode operating mode of the semiconductor arrangement in one embodimentbelow the edge region.

FIG. 6A illustrates, for a semiconductor component according to FIGS. 2Aand 2B, p-type zones 28 a-d disposed upstream of the n-type emitterzones 13 in possible embodiments. These p-type zones 28 a-d disposedupstream have a high doping concentration and can be wider (cf. zones 28b, 28 c) or narrower (cf. zones 28 a, 28 d) than the adjoining n-typeemitter zone 13. They can lie within (cf. zones 28 a, 28 b) the fieldstop zone 17 or project beyond the latter (cf. zones 28 c, 28 d). Thesep-type zones 28 a-d disposed upstream form additional diodes with highlydoped p- and n-type zones in the semiconductor arrangement. They bringabout an increase in the diode softness and ensure the reestablishmentof a current in the case of current chopping as a result of too littleresidual plasma in the semiconductor structure.

FIG. 6B illustrates a distribution of the electric field strengthbetween front side Vo and rear side Rü of the semiconductor component ina section through a front-side p-type zone, a drift region, a p-typezone disposed upstream as in FIG. 6A, and a rear-side n-type emitterzone during the turn-off or depletion of the diode, at the time when thecharge carriers have been depleted in the zone between the body region 4and a p-type zone 28 d disposed upstream. The sectional course betweenfront side Vo and rear side Rü is illustrated at the top on the right inthe figure. The curve profile illustrates a commencement and a rise ofthe electric field within the front-side p-type zone as far as theadjoining drift region, in which the field strength decreases relativelyas far as the in turn adjoining p-type zone disposed upstream, butwithout being totally extinguished. Within the p-type zone disposedupstream, the field strength rises again to the rear-side n-type emitterzone and can reach larger values than within the front-side p-type zoneor the drift zone. Within the rear-side n-type emitter zone, the fieldstrength finally decreases and tends toward zero. If a current flowwithin the drift zone threatens to undergo chopping, the p-type zonedisposed upstream ensures, by using at least one diode formed by ap-type zone disposed upstream and a rear-side n-type emitter zone, thata current flow is maintained because additional charge carriers aregenerated by avalanche generation when a critical field strength of2·10⁵ V/cm to 5·10⁵ V/cm is reached.

FIG. 7A illustrates the diode operating mode of a semiconductorcomponent according to FIGS. 2A and 2B in the diode operating mode,wherein at least one additional zone 29 can be arranged in the driftzone 2. The at least one zone 29 can have a greatly reduced chargecarrier lifetime. Its area extends, in this example, over the region ofcharge carrier flooding in the diode operating mode, that is to say overthe effective diode area. On account of an approximately frustoconicalpropagation characteristic of the charge carrier flooding within thedrift zone 2, the area extent of the zone 29 can vary depending on itsposition within the drift zone 2. A size of the at least one additionalzone 29 can be chosen such that it completely covers the region of thecharge carrier throughflow in the diode operating mode. The zone 29 canrestrict the charge carrier flooding in the diode operating mode. Theswitching power loss of the semiconductor component can thereby bereduced. The regions 2 a and 2 b and/or 3 b can have a non-reduced or aweakly reduced charge carrier lifetime in contrast to the zone 29,wherein charge carriers flow through the regions 2 b in contrast to theregions 2 a in the diode operating mode.

Another embodiment of the at least one zone 29 having a reduced chargecarrier lifetime is illustrated in FIG. 7B. Here the zone 29 is arrangedcontinuously within the drift zone 2 and can serve the same purpose asin FIG. 7A. The regions 2 a and 2 b can likewise have a weakly reducedcharge carrier lifetime or a non-reduced charge carrier lifetime, whilethe regions 3 a and 3 b do not have a reduced charge carrier lifetime.

FIGS. 8A to 8D illustrate plan views of cell regions of semiconductorstructures according to FIGS. 2A and 2B with the underlying n-typeemitter zones 13. In this case, the at least one effective diode area 30in FIG. 8A covers a portion of the cell region 3. These portions becomesmaller and smaller in FIGS. 8B to 8C. Two groupings of the n-typeemitter zones 13 are illustrated in FIG. 8D.

FIGS. 9A to 9J likewise illustrate plan views of cell regions ofsemiconductor structures according to FIGS. 2A and 2B with underlyingn-type emitter zones 13. The edge regions 10, the cell regions 3 and then-type emitter zones 13 are illustrated in each case. FIG. 9Aillustrates a second region 19 without n-type zones 13 containedtherein, while FIG. 9B illustrates the corresponding subregion 33, inwhich no charge carrier throughflow takes place in the diode operatingmode. Analogously to this, FIGS. 9C and 9D, 9E and 9F, and 9G and 9H,illustrate the second regions 19 without n-type emitter zones 13 and,respectively, the subregions 33 without charge carrier throughflow inthe diode operating mode. For illustration purposes, circular areas aredepicted as partial areas, which circular areas are enclosed by thesurface or surfaces of the at least one second region 19, which form thesubregions 33. FIG. 9I illustrates second regions 19 and an n-typeemitter zone elongated over a length of the cell region 3. FIG. 9Jillustrates a first region 18, which can contain an elongated n-typeemitter zone as in FIG. 9I, or else a plurality of distributed n-typeemitter zones. The illustration additionally illustrates two secondregions 19 and also circular areas contained therein, for illustratingpossible subregions 33.

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat a variety of alternate and/or equivalent implementations may besubstituted for the specific embodiments shown and described withoutdeparting from the scope of the present invention. This application isintended to cover any adaptations or variations of the specificembodiments discussed herein. Therefore, it is intended that thisinvention be limited only by the claims and the equivalents thereof.

1. A semiconductor component comprising: a semiconductor body having acell region, provided with at least one zone of a first conduction typeand at least one zone of a second conduction type in a rear side; and adrift zone of the first conduction type in the cell region, the driftzone containing at least one region through which charge carriers flowin an operating mode of the semiconductor component in one polarity andcharge carriers do not flow in an operating mode of the semiconductorcomponent in an opposite polarity.
 2. The semiconductor component ofclaim 1, wherein the drift zone contains a single further region throughwhich charge carriers flow in an operating mode of the semiconductorcomponent in the one polarity and in an operating mode of thesemiconductor component in the opposite polarity.
 3. The semiconductorcomponent of claim 1, comprising wherein the drift zone contains atleast one further region through which charge carriers flow in anoperating mode of the semiconductor component in the one polarity and inan operating mode of the semiconductor component in the oppositepolarity.
 4. The semiconductor component of claim 1, comprising whereinthe operating mode of the semiconductor component in the one polarity isan IGBT operating mode of the semiconductor component and the operatingmode of the semiconductor component in the opposite polarity is a diodeoperating mode of the semiconductor component.
 5. The semiconductorcomponent of claim 1, comprising wherein charge carriers do not flowthrough an edge region in the diode operating mode of the semiconductorcomponent.
 6. The semiconductor component of claim 1, comprising whereinthe entire effective diode area formed from one or a plurality of thearea(s) flooded by charge carriers in the diode operating mode of thesemiconductor component is smaller than the area of the cell region. 7.The semiconductor component of claim 1, comprising wherein the effectivearea of the diode is arranged completely in the cell region and does notgo beyond an edge region.
 8. The semiconductor component of claim 1,comprising wherein the effective area of the diode is between 25% and75% of an area of the cell region.
 9. The semiconductor component ofclaim 1, comprising wherein the effective area of the diode has nooverlap with an edge region adjacent to the cell region.
 10. Asemiconductor element comprising: a semiconductor body having a cellregion, with at least one zone of a first conduction type and at leastone zone of a second conduction type in a rear side and contains a driftzone of the first conduction type in the cell region; wherein the rearside contains both at least one region having zones of the first and ofthe second conduction type and at least one further region of the secondconduction type which has, as partial area, at least one circular areahaving a diameter of at least four times a thickness of the drift zoneand which contains no zones of the first conduction type.
 11. Thesemiconductor component of claim 10, comprising wherein a dopingconcentration in the at least one zone of the first conduction type isincreased in comparison with a doping concentration of the drift zone.12. The semiconductor component of claim 10, comprising wherein in theat least one zone of the first conduction type, a doping concentrationis achieved by using a doping dose of between 1015 1/cm2 and 1016 1/cm2.13. The semiconductor component of claim 10, comprising wherein alaterally delimited further zone of the second conduction type isarranged directly in front of the at least one zone of the firstconduction type.
 14. The semiconductor component of claim 10, comprisingwherein a field punch-through at the at least one further zone makes itpossible to prevent a chopping of a current flow in the event of a risein an electric field at a diode comprising the zone of the firstconduction type.
 15. The semiconductor component of claim 10, comprisingwherein the drift zone of the first conduction type comprises at leasttwo zones having different charge carrier lifetimes.
 16. Thesemiconductor component of claim 15, comprising wherein one zone has agreatly reduced charge carrier lifetime in comparison with that in thezone.
 17. The semiconductor component of claim 15, comprising whereinone zone is a local zone in the vertical direction having a greatlyreduced charge carrier lifetime in comparison with that in the zone andthe drift zone has a second zone having a weakly reduced charge carrierlifetime in comparison with that in the zone.
 18. A semiconductorcomponent comprising: a semiconductor body having a cell region and anedge region, which semiconductor body, at least in the cell region,contains a drift zone of a first conduction type in a front side of thesemiconductor body and is provided with at least one zone of the firstconduction type and at least one zone of the second conduction type in arear side; wherein a doping concentration in the at least one zone ofthe first conduction type is increased to such a great extent incomparison with a drift zone doping concentration such that a softnessof a diode comprising the at least one zone of the first conduction typeis ensured.
 19. The semiconductor component of claim 18, comprisingwherein in the at least one zone of the first conduction type, thedoping concentration is achieved by a doping dose of between 1015 1/cm2and 1016 1/cm2.
 20. A semiconductor component comprising: asemiconductor body having a cell region and an edge region, whichsemiconductor body, at least in the cell region, contains a drift zoneof a first conduction type in a front side of the semiconductor body andis provided with at least one zone of the first conduction type and atleast one zone of a second conduction type in a rear side; and wherein alaterally delimited further zone of the second conduction type isarranged directly in front of the at least one zone of the firstconduction type.
 21. The semiconductor component of claim 20, comprisingwherein a chopping of the current of the diode can be prevented by usinga pn junction of the zones.
 22. The semiconductor component of claim 20,wherein the drift zone of the first conduction type comprises at leasttwo zones having different charge carrier lifetimes.
 23. Thesemiconductor component of claim 20, comprising wherein one zone has agreatly reduced charge carrier lifetime in comparison with that in thezone and a second zone having a weakly reduced charge carrier lifetimein comparison with that in the zone is arranged in the drift zone.
 24. Amethod for producing a semiconductor element, including a semiconductorbody having a cell region comprising: forming in the cell region of thesemiconductor body a drift zone of a first conduction type; forming atleast one region having exclusively zones of a second conduction type ona rear side of the semiconductor body; and forming at least one regionhaving zones both of the first conduction type and of the secondconduction type on the rear side, wherein the at least one region havingzones of the second conduction type has as a partial area at least onecircular area having a diameter of at least four times a thickness ofthe drift zone and contains no zones of the first conduction type.